libmultipath: Add mpath_bdev_get_unique_id()

Add mpath_bdev_get_unique_id() as a multipath block device .get_unique_id
handler.

Signed-off-by: John Garry <john.g.garry@oracle.com>

Author: johnpgarry

include/linux/multipath.h

@@ -86,6 +86,8 @@ struct mpath_head_template {
 				 unsigned int poll_flags);
 	enum mpath_iopolicy_e (*get_iopolicy)(struct mpath_head *);
 	struct bio *(*clone_bio)(struct bio *);
+	int (*get_unique_id)(struct mpath_device *, u8 id[16],
+				enum blk_unique_id type);
 	const struct mpath_pr_ops *pr_ops;
 	const struct attribute_group **device_groups;
 };

lib/multipath.c

@@ -496,6 +496,22 @@ static void mpath_bdev_release(struct gendisk *disk)
 	mpath_put_disk(mpath_disk);
 }
 
+static int mpath_bdev_get_unique_id(struct gendisk *disk, u8 id[16],
+    enum blk_unique_id type)
+{
+	struct mpath_disk *mpath_disk = mpath_gendisk_to_disk(disk);
+	struct mpath_head *mpath_head = mpath_disk->mpath_head;
+	int srcu_idx, ret = -EWOULDBLOCK;
+	struct mpath_device *mpath_device;
+
+	srcu_idx = srcu_read_lock(&mpath_head->srcu);
+	mpath_device = mpath_find_path(mpath_head);
+	if (mpath_device)
+		ret = mpath_head->mpdt->get_unique_id(mpath_device, id, type);
+	srcu_read_unlock(&mpath_head->srcu, srcu_idx);
+
+	return ret;
+}
 static int mpath_bdev_ioctl(struct block_device *bdev, blk_mode_t mode,
 		    unsigned int cmd, unsigned long arg)
 {
@@ -704,6 +720,7 @@ const struct block_device_operations mpath_ops = {
 	.submit_bio	= mpath_bdev_submit_bio,
 	.ioctl		= mpath_bdev_ioctl,
 	.compat_ioctl	= blkdev_compat_ptr_ioctl,
+	.get_unique_id	= mpath_bdev_get_unique_id,
 	.report_zones	= mpath_bdev_report_zones,
 	.getgeo		= mpath_bdev_getgeo,
 	.pr_ops		= &mpath_pr_ops,